1. Field of the Invention
The present invention relates to dental devices that are worn on an arch of teeth, and in particular, to devices that can deliver a beneficial agent to, and protect the teeth and soft tissues from mechanical, chemical and biologic injury.
2. Description of Related Art
Mouthguards are typically made from plastics materials such as an ethylene vinyl acetate copolymer (EVA). Other devices such as dentoalveolar trays, carriers and splints may be made of EVA or other biocompatible plastic material. There are several categories of mouthguards: Mouthguards that are stock pre-molded products and made in a variety of sizes, home or self-moldable to suit the physical characteristics of the user, or custom molded by a dentist or other professional to suit the characteristics of the user. Regarding physical protection, stock mouthguards are typically the cheapest and least effective in use while the custom molded and shaped mouthguards are the most expensive and effective in their impact absorbent properties.
Athletes in many sports wear mouthguards for prolonged periods. It is common knowledge that when these athletes engage in strenuous physical activity, they lose and must replace significant amounts of fluids, nutrients and calories. In order to hydrate themselves, and replenish their energy, athletes must drink large quantities of fluids and eat foods that are very often cariogenic. These cariogenic fluids and materials cover the teeth, and when a mouthguard is inserted afterwards, the teeth are acted upon by cariogenic bacteria in an ideal environment, shielded from the buffering ability of saliva. In athletes, factors that serve to diminish salivary flow around the teeth include the general sympathetic tone of the nervous system, dehydration and shielding of the teeth by a mouthguard. Moreover, the elderly, patients suffering from a variety of autoimmune diseases, patients on a variety of medications and patients treated in the head region with external beam radiation may also suffer from reduced salivary flow. Whatever the cause, reduced salivary flow greatly increases the incidence of dental caries and periodontal disease.
U.S. Pat. No. 4,920,984 relates to a mouthguard material that may be custom shaped or molded employing a teeth impression cast pressed against softened thermoplastic sheet material that increases in thickness from one end to the other.
Australian patent specification 633269 discloses a mouthguard made from an EVA copolymer having a softening point higher than the normal temperature of an oral cavity but lower than the highest temperature that the oral cavity can endure so that the user may adapt the mouthguard to fit the mouth by biting onto it after it has been heated. The shaping procedure may be repeated if the shape or configuration of the teeth should change.
In FIG. 15 of U.S. Pat. No. 5,082,007 a gel or fluid capsule is contained between the upper and lower portions of a mouthguard. The nature of this gel is not described and appears to serve a mechanical, that is, a shock absorbing function.
It is not only known to employ materials enabling custom or self shaping of mouthguards, it has been suggested that mouthguards use other additives in the material of construction to enhance the characteristics of the material. For example, in U.S. Pat. No. 4,044,762 an athletic mouthguard is formed from a mixture of a plastic resin (e.g., an ethylene vinyl acetate that can be heated and softened to form a custom-fitted impression) and a fluoride compound that protects the wearer's teeth. As an alternative, the reference suggests spraying or otherwise coating the surface of a mouthguard with a fluoride compound. This fluoride compound is gradually delivered while the mouthguard is worn.
In FIGS. 7 and 8 of U.S. Pat. No. 5,323,787 a medicated pad is adhesively secured on the occlusal surface of a mouthpiece to treat the teeth and gums. The pad is saturated with a medicating substance in an intermediate layer of absorbent polymeric or fabric material, and that intermediate layer is overlaid with a non-porous outer layer. The pad can either be replaced or soaked to renew the medication. Specific medications are not discussed, although for other embodiments the mouthpiece is soaked in sterilizing (bactericides) and mouth-refreshing ingredients such as flavorings of the type used in conventional mouthwashes.
German patent specification 401 1204 discloses a mouthguard material consisting of an EVA copolymer material, polycaprolactone and colorants and perfumes and PVA (polyvinyl acetate) to reduce the softening point of the resultant mouthguard for ease of manipulation and shaping.
In U.S. Pat. No. 5,395,392 an infant's pacifier has a perforated mouth bulb containing an powder, syrup, or tablet with an agent such as monoclonal antibodies, fluorides, sorbitol, or xylite (xylitol).
Xylitol is a naturally occurring sugar. It is a five-carbon polyalcohol, pentitol, which is widely distributed in nature. Most fruits, berries and plants contain xylitol. Xylitol is also an intermediate of mammalian carbohydrate metabolism. Our bodies produce up to 15 grams of xylitol from other food sources using established energy pathways. Xylitol use is known to reduce tooth decay rates both in high-risk groups (high caries prevalence, poor nutrition, and poor oral hygiene) and in low risk groups (low caries incidence using all current prevention recommendations). Sugar-free chewing gums and candies made with xylitol as the principal sweetener have already received official endorsements from numerous international dental associations. Studies using xylitol as either a sugar substitute or a small dietary addition have demonstrated a dramatic reduction in new tooth decay, along with arrest and even some reversal of existing dental caries. Xylitol provides additional protection that enhances all existing prevention methods. This xylitol effect is long lasting and possibly permanent. Low decay rates persist even years after the trials have been completed.
For the anticariogenic activity of casein phosphopeptides, see U.S. Pat. Nos. 5,015,628; 5,834,427 (method of preparing casein phosphopeptides); and 5,981,475. For various remineralizing compositions, see U.S. Pat. Nos. 4,348,381; 5,562,895; 5,895,641; and 6,036,944.
For various mouthguards and similar dental devices, see U.S. Pat. Nos. 4,554,154 (plastic that is chewable or usable as dental floss carries remineralizing, immunological, and anti-bacterial agents; e.g. sodium fluoride, chlorhexidine and lysozyme); 5,085,585 (U-shaped applicator is placed over teeth to apply medicaments to teeth and gum pockets); 5,194,003 (device that fits over teeth releases beneficial agents from a reservoir); 5,339,832 (composite mouthguard with integral shock-absorbing framework); 5,365,624 (mouthpieces with cleaning motors or gum cushioning material); and 6,012,919 (occlusal protector pad in an athlete's dental appliance has an upper layer of EVA and polycaprolactone).
Certain hydrogels, particularly synthetic hydrogels, can act as carriers for drugs and other active agents. These hydrogels allow passage of the agent, in some cases acting as a membrane that allows agent passage. Covalently crosslinked hydrogels can incorporate a drug or other agent during the polymerization step; or the agent can be loaded from a solution. These types of hydrogels tend, however, to be weak when swollen by its water content. With thermoplastic (solvent soluble) hydrogels, an agent or drug can be compounded with the polymer during extrusion or injection molding; or by combining the agent with the polymer solution in a suitable solvent. See “Hypan® Hydrogels” published by Hymedix International, Inc. The Hypan® hydrogels can be obtained with varying degrees of hydrophilicity. They can also be obtained either as relatively hard, crystalline blocks, used for structural applications; or as meltable transient clusters that are highly swelling, and useful as emulsifiers, gelling agents, and drug carriers. Various other suppliers of hydrogel exist as well.
For hydrogels with improved stability, see U.S. Pat. No. 5,346,935. See also U.S. Pat. Nos. 5,071,657 (transdermal administration of a medicinal agent dissolved in a nonflowable gel distributed in a microdisperse mode in a crosslinked silicone elastomer); 5,200,194 (oral osmotic device has a beneficial agent and hydrophilic support fibers inside a semi-permeable membrane); and 5,252,692 (hydrophilic acrylic copolymers).
See also, U.S. Pat. Nos. 3,996,934 (bandage using microcapsules to deliver a drug); 5,366,935; 5,286,490 (transdermal patch delivers fluoride medication to treat osteoporosis or periodontal disease); and 5,925,372 (transdermal delivery system for ethanol soluble drugs).
Thus, while prior art devices are capable of delivering an agent to surfaces within the oral cavity, they lack the ability to deliver agents to selected surfaces within the oral cavity, or to deliver one or more agents to different oral surfaces simultaneously. The present invention fulfills this long-felt need by being able to selectively deliver agents to specific oral surfaces, and to be able to deliver multiple agents to different surfaces using a single device, which device includes numerous insets for receiving agent-containing inserts therein. This agent delivery function can be performed either independently of, or in conjunction with, the protective functions of the present invention, which can also act as an athletic mouthguard. Further, the present invention provides a means to recharge the device with an agent once that agent has been depleted.